Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $203.57   5.554%   $214.8763   $214.88   $214.90   $214.90  
  Purchase #2 $205.27   12.138%   $230.1857   $230.19   $230.20   $230.20  
  Purchase #3 $212.49   5.490%   $224.1557   $224.16   $224.15   $224.20  
  Purchase #4 $22.54   10.547%   $24.9173   $24.92   $24.90   $24.90  
  Purchase #5 $156.99   4.628%   $164.2555   $164.26   $164.25   $164.30  
  Purchase #6 $192.89   3.273%   $199.2033   $199.20   $199.20   $199.20  
  Purchase #7 $175.47   13.207%   $198.6443   $198.64   $198.65   $198.60  
  7 purchase totals = $1,169.22       $1,256.2381   $1,256.25   $1,256.25   $1,256.30